Winter 2013-14 medium range discussion

[Ji]

donald?

 

ftp://ftp.cdc.noaa.gov/Public/gbates/reforecast2/teleconn/4panel.png

[NJwinter23]

Yeah, it's definitely a waiting game this side of the pond, that's for sure. I don't think many would be disappointed if a repeat of Feb 91 did happen, as, for example, it produced the following synoptics;

 

http://www.wetterzentrale.de/pics/archive/ra/1991/Rrea00119910207.gif

 

As is usually the case, some who crave winter cold are already writing it off because of the up coming patterns, but clearly on the 11th of December that's crazy talk. A long way to go and particularly given the events of back in March of this year, primarily down to the SSW, March can sometimes provide a "winter lifeline" under the right synoptics. It's a case of sit and wait to hopefully see a gradual change in the evolution of the broader synoptic patterns, hope for some mountain torque events as well, so get some wave 1 and 2 activity going. I have a feeling, given current situations, that this polar vortex this winter season is going to take some 'beating down', it sure is noteworthy and 'powerful' at the present time, clearly not just within the trop but well up into the strat as well.

 

Cheers, Matt.

 

Yup just need to hang on tight for now. At least your weather still can be interesting with a +NAO...massive cyclones and wind storms despite the milder atlantic influence..our upstream equivalent, the EPO is extremely warm and boring weather for us when +

[donsutherland1]

donald?

 

ftp://ftp.cdc.noaa.gov/Public/gbates/reforecast2/teleconn/4panel.png

I just got back from Philly (where the snow was) and haven't had enough time to really look at the guidance in great detail, but will be doing so in the next day or so. Let's hope the ensembles are correct in holding the EPO-. If so, December might just end on a cold note. Additional opportunities for snowfall would be nice, including in areas that have not yet received much snowfall to date.

[donsutherland1]

Some morning thoughts...

 

The EPO and AO remain remarkably stable at their respective negative and positive states. The ensemble guidance shows little meaningful change from those states, even as their values are forecast to change. However, if one is looking for a possible evolution that could have longer-term implications, the ensemble guidance has slowly been shifting from persistent PNA- values to neutral values. Some ensemble members even point to the development of a weakly positive PNA.

 

 

If the PNA does, in fact, evolve as currently shown on the ensembles, the stage could be set for widespread cold anomalies in North America for the closing week of December. Moreover, a number of winters that saw such an evolution wound up with a cold January in Canada and parts of the northern CONUS. Hence, the potential evolution might have implications beyond the close of December.

 

For now, those are ensemble forecasts. But at least one possible evolution would lead to cold and possible opportunities for snowfall, especially if ENSO Region 3.4 (current anomaly of +0.2°C experiences additional warming as the winter progresses).

[tacoman25]

Behold the power of -EPO. Coast to coast cold.

 

 

[Damage In Tolland]

Behold the power of -EPO. Coast to coast cold.

 

 

30dTDeptUS.png

Pacific always, trumps the Atlantic..Always

[wxmx]

A lot less the further east you go, where a good Atlantic can trump a bad Pacific

[bluewave]

Warmest SST's on record for this time of year in that spot under the long duration -EPO ridge.

The ridge that has been dominating the area around Alaska this year to date has surpassed

the previous 500 mb record years of 1957 and 1989.

 

 

 

 

 

[WinterWxLuvr]

Pacific always, trumps the Atlantic..Always

Makes sense. It's upstream.

[OKpowdah]

Pacific always, trumps the Atlantic..Always

 

Except when it comes to highly amplified disturbances, which is really when you're concerned anyway if you want big snow.

 

Pacific is great in dictating the arctic connection to the US, but the Atlantic dictates the evolution of s/w's across the US ... do they break into the Great Lakes, or does downstream forcing trump nonlinear growth.

[donsutherland1]

December 23-31, 2013 Thoughts:

 

In terms of teleconnections, the ensembles continue to favor a predominant EPO-, AO+, PNA+ regime during the closing days of December. At the same time, a large area of cold continues to cover North America and there is little evidence that the cold will be driven from North America anytime soon. Consequently, areas adjacent to the cold will likely wind up colder than normal, as well, even if 500 mb pattern might be expected to have some warmth into those areas.

 

Below are a number of charts showing the temperature anomalies associated with the forecast ENSO-teleconnections, teleconnections alone, GFS ensembles, and NAEFS.

 

 

Continuity with the predominant pattern since November argues that the areas of warmth could be more limited than depicted on some of the above charts. There also remains a distinct possibility of an Arctic outbreak sometime during the 12/23-31 period with perhaps the coldest anomalies focused on the Plains States into central Canada.

 

In terms of overall anomalies for the 12/23-31 period, my thoughts are as follows:

 

Much of Canada: Colder than normal

Northern and Central Plains: Colder than normal

Great Lakes Region/Ohio Valley: Colder than normal

Pacific Northwest: Near normal

New England and the Middle Atlantic Region: Colder than normal

Southeast/Gulf States: Warmer than normal

Southern Plains (including Texas): Somewhat cooler than normal to near normal

Desert Southwest: Warmer than normal

[MattHugo81]

Might be scraping the bottom of the barrel here, but perhaps just some signs at the far end of the ECM model of increased wave 2 activity;

 

http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/ecmwfzm_ha2_f240.gif

http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/ecmwfzm_ta2_f240.gif

 

Some interest down to around 3hPa;

 

http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/ecmwf3f240.gif

 

However, down at 30hPa, the vortex is as solid as a rock;

 

http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/ecmwf30f240.gif

 

Obviously ECM model under-went model upgrades in November with better resolution and capturing the strat, so something to keep an eye on. GWO looks insignificant, with nothing significant really showing up, so not sure whether anything can be picked out from that in terms of possible mountain torque events within the next 7 to 14 days say;

 

http://www.atmos.albany.edu/student/nschiral/research/gwo/gfsgwo_1.png

 

500mb heights from both GFS and ECM are extreme in terms of just how low pressure is likely to get within the North Atlantic and around Greenland in general;

 

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

 

Here's hoping that wave 2 activity increases, its about time the vortex took a few 'punches', but as I said the other day, looks like it's going to take a lot to beat this one down.

 

Regards from the UK

 

Matt.

[bluewave]

This may be the first time that the AO has been +4 in both November and December if the model is correct.

It's like mother nature just flipped the AO switch after the lowest March reading on record of -3.185. This

year has experienced as dramatic a pattern change as we are ever going to see.

 

 

 

[DaculaWeather]

There have only been 2 Novembers that had 2 or above, 1978 at 2.470 and this November at 2.029. There have only been 2 Decembers at 2 or above so far... 2006 at 2.282 and 2011 at 2.221. 

[bluewave]

There have only been 2 Novembers that had 2 or above, 1978 at 2.470 and this November at 2.029. There have only been 2 Decembers at 2 or above so far... 2006 at 2.282 and 2011 at 2.221. 

 

The new model that was run in November 2012 at the Met Office really seemed to capture the pattern change. I will be waiting

to see what the new long range forecast looks like when they post it in January. That cold pool

forecast for SW of Iceland matched the +AO/+NAO signature.

 

http://www.metoffice.gov.uk/research/news/decadal-forecasting

 

http://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/long-range/decadal-fc

 

 

 

 

[donsutherland1]

This may be the first time that the AO has been +4 in both November and December if the model is correct.

It's like mother nature just flipped the AO switch after the lowest March reading on record of -3.185. This

year has experienced as dramatic a pattern change as we are ever going to see.

 

2013 is, in fact, the first time the AO has had +4 readings in both November and December.

[donsutherland1]

Mid-Month Update:

 

To date, the month has been characterized by an EPO-/AO+ pattern. Today, the AO was +4.201. That breaks the daily record high of +3.159, which was set in 2006. Nevertheless, unlike 2006, a snowstorm brought more than a foot of snow across parts of Maine. In 2006, the EPO was +1.589. Today, it was approximately -1.3.

 

Nevertheless, the ensembles have been hinting that the EPO could become more neutral as December winds down.

 

 

To date, the predominant EPO/AO pattern has produced outcomes fairly close to those shown for the partial teleconnection cases (excluding ENSO) for the month of December (Message #204 of 11/30). If, however, the more neutral EPO materializes, one could see the cold anomalies lift into Canada, and milder anomalies prevail, on average, during January. The 360-hour reforecast ensembles hint at a possible pattern evolution toward a milder January outcome. Fortunately, at this point in time, the skill level of both is low.

 

 

Finally, the snowfall that has blanked parts of the northern Mid-Atlantic this month, including the snowfall that appears likely on Tuesday courtesy of two clipper systems racing eastward, is providing a hint that the northern Mid-Atlantic region into southern New England may experience normal to above normal snowfall for the winter. For example, Philadelphia has already received 11.1" snow this month. 8/9 (89%) of winters that received 10" or more snowfall in December since 1872 wound up with 20" or more seasonal snowfall. and 6/9 (67%) had 30" or more. The sample size is small, but the probability is very high, so odds probably lean toward a winter with 20" or more snowfall.

[donsutherland1]

Quick morning thoughts...

 

The EPO has now been negative for 39 consecutive days. The most prolonged negative EPO regime that commenced in November was 45 days (2010). The latest ensembles show the EPO going weakly positive around or just after 12/22, but perhaps only temporarily.

 

The AO is now above +4.000 for the second consecutive day. The AO will very likely remain positive for at least the next 1-2 weeks.

 

The near-term excitement will concern a clipper system (possibly with a second weaker disturbance on its heels) that should bring a fairly wide 1"-3" snowfall across parts of the northern Mid-Atlantic region and across a large swatch of southern and central New England. This system appears to be more robust than most clipper systems, so it could tap Atlantic moisture producing some areas of 3"-6" snowfall. Where those enhanced areas of snowfall set up are difficult to pin down. Trying to do so is a lot like trying to pinpoint where thunderstorms will pop up on a humid summer day. Nevertheless, a portion of southern New England might have the highest chance of seeing such enhanced snowfall.

[Wow]

Record longest +AO streak was in 1990, from 1/20/90 to 5/19/90 (120 days).  Save for 4 days, from 12/22/89 to 5/19/90, the AO was positive.  On the flip side, the record longest -AO streak was in 1960, from 12/25/59 to 4/4/60 (102 days).

[Heisy]

What are some things we would hope to happen to get a -AO to form? Like I know I've heard large GL Cutters can help build the NAO, but I'm not sure. Does the MJO correlate to the AO at all? Don are you seeing any signs of a block forming in Jan? 

[Chinook]

Mid-Month Update:

 

To date, the month has been characterized by an EPO-/AO+ pattern. Today, the AO was +4.201. That breaks the daily record high of +3.159

 

Icelanders are losing their hats. Not enough pressure to hold them on. Check out this UK map from a couple of days ago.

 

 

 

[REDMK6GLI]

Icelanders are losing their hats. Not enough pressure to hold them on. Check out this UK map from a couple of days ago.

UK_met_office_surface_map.gif

WOW! That is impressive, so some -NAO would really help them out huh? Lol

[tacoman25]

Can someone remind me again of the demonstrated skill for the Euro weeklies 3-4 weeks out?

[donsutherland1]

Can someone remind me again of the demonstrated skill for the Euro weeklies 3-4 weeks out?

Here's some info. that I found: http://www.ecmwf.int/newsevents/meetings/forecast_products_user/Presentations2013/Posters/Vitart.pdf

[tacoman25]

Here's some info. that I found: http://www.ecmwf.int/newsevents/meetings/forecast_products_user/Presentations2013/Posters/Vitart.pdf

 

Thanks, Don!

[donsutherland1]

What are some things we would hope to happen to get a -AO to form? Like I know I've heard large GL Cutters can help build the NAO, but I'm not sure. Does the MJO correlate to the AO at all? Don are you seeing any signs of a block forming in Jan? 

Nothing yet, unfortunately. The AO+ might become more relaxed for at least a time, though if some of the guidance is correct.

[ayuud11]

hey Don,are you expecting a repeat of 07-08 winter in terms of synoptic storm tracks up here in WNY/Srn ontario region? 

[donsutherland1]

hey Don,are you expecting a repeat of 07-08 winter in terms of synoptic storm tracks up here in WNY/Srn ontario region? 

It's difficult to try to pinpoint storm tracks. Neither ensembles nor analogs provide much insight into such storm tracks.

 

However, December snowfall patterns can offer some insight. With today's clipper system, PHL, NYC, and BOS will very likely reach 8" or more snowfall for December (PHL is already there). Looking westward to Buffalo, such years have seen 50% with 80" or more seasonal snowfall in Buffalo and 50% less than 80" seasonal snowfall.

 

For the winters with less than 70" snowfall: December snowfall: < 20" (4/4 cases)

For the winters with less than 80" snowfall: December snowfall: < 25" (5/6 cases)

For the winters with 80" or more snowfall: December snowfall: 25" or more (5/6 cases)

For the winters with 100" or more snowfall: December snowfall: 25" or more (4/4 cases)

 

December snowfall through 12/16 was 16.6". The cold shot that appears likely after this weekend might produce some meaningful lake effect snows to boost that figure. The GFS shows an even stronger cold shot before the end of December, so there might be another opportunity for lake effect snow. Lighter synoptic snows might coincide with the frontal passages.

[donsutherland1]

December snowfall in parts of the Middle Altantic and New England regions has been similar to what has occurred in winters that proved snowy, particularly in Philadelphia and New York City. Through December 16, monthly snowfall was as follows:

 

Boston: 5.0"

New York City: 7.1"

Philadelphia: 11.1"

 

Following today's clipper system, both Boston and New York City will likely have reached or exceeded 8" of snow for December. Going back to 1888, there were 12 years during which December snowfall reached 8" or more in Boston, New York City, and Philadelphia. Those years and seasonal snowfall for Boston, New York City, Philadelphia, and Washington, DC are listed below. It should be noted that monthly snowfall in Washington, DC is currently lower than it was for all 12 cases, so that creates greater uncertainty aside from the relatively small sample that is involved.

 

[REDMK6GLI]

December snowfall in parts of the Middle Altantic and New England regions has been similar to what has occurred in winters that proved snowy, particularly in Philadelphia and New York City. Through December 16, monthly snowfall was as follows:

 

Boston: 5.0"

New York City: 7.1"

Philadelphia: 11.1"

 

Following today's clipper system, both Boston and New York City will likely have reached or exceeded 8" of snow for December. Going back to 1888, there were 12 years during which December snowfall reached 8" or more in Boston, New York City, and Philadelphia. Those years and seasonal snowfall for Boston, New York City, Philadelphia, and Washington, DC are listed below. It should be noted that monthly snowfall in Washington, DC is currently lower than it was for all 12 cases, so that creates greater uncertainty aside from the relatively small sample that is involved.

 

 

that's pretty encouraging to say the least don. the way the -EPO is cooperating but the AO/NAO and PNA aren't its going to be a battle to get that ideal setup we need for those nice east coast winter storms. I guess by the end of this month we'll know more as to what to expect for atleast the first half of January. your forecasts/analysis have been pretty accurate as well